THE NATURE OF DISEASE

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THE NATURE OF DISEASE
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Immune System

• The immune system of the human body is made up
  of 
• Cells
• Molecules
• Organs
• that act together to defend the body against
  foreign invaders that may cause disease.
• The health of the body is dependent on the immune
  systems ability to recognize and then repel or
  destroy these invaders
• It is designed to defend you against millions of
  bacteria, microbes, viruses, toxins and parasites
  that can invade your body.

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PATHOGENS

• Pathogens disease causing agents
• Ex. Bacteria, Viruses, Parasites
• Pathogens are found in soil, contaminated water,
  and infected animals, including other people

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Birth

• Before you are born your body is free of
  pathogens.
• At birth microorganisms establish themselves on
• your skin
• respiratory system
• urinary system
• reproductive system
• intestinal tract

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INFECTIOUS DISEASES

• Infectious Diseases any disease caused by the
  presence of a pathogen in the body
• These microorganisms have a symbiotic
  relationship with your body
• However, if you become injured or weak these same
  organisms can become pathogens.

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• EX. ZOONOSIS An infectious disease transmissible
  under natural conditions between animals and
  human.

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Examples of Infectious Diseases
Disease Cause Affected Organ System Transmission
Smallpox Virus Skin Droplet
Colds Virus Respiratory Direct contact
Influenza Virus Respiratory Droplet
Food Poisoning Bacteria Digestive Contaminated food
Rabies Virus Nervous Animal bite
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What causes a disease?

• Not all disease are caused by pathogens
• Example Hemophilia- recessive allele on the X
  chromosome
• Pathogens can also cause some cancer

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Robert Koch

• Robert Koch 1876 discovered that pathogens caused
  disease
• Studying Anthrax
• Would inject it into animals, they would get sick
  then he would isolate the bacteria in their blood
  and compare them to the anthrax he isolated from
  other victims.

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Reservoirs of Pathogens

• Living Reservoirs
• People often carrier a pathogen and pass it to
  others without knowing it
• Animals can also pass on the flu or rabies to
  humans
• Nonliving Reservoirs
• Soil contains pathogens such as fungi and
  bacteria that can cause food borne illnesses
• Water contaminated with human waste contains
  bacteria that cause intestinal illnesses

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Transmission

• Pathogens are transmitted to humans by
• Direct Contact (Examples to Follow)
• Through an Object
• Doorknob, Tabletop, Faucet handle
• Through the Air
• Coughing and Sneezing
• Through an Intermediate Organism
• Fleas, Ticks, Mosquitoes, Rats

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Transmission

• Direct contact
• An easy way to catch most infectious diseases is
  by coming in contact with someone who has one.
  This "someone" can be a person, an animal or, for
  an unborn baby, its mother.
• Person to person.
• Most common- direct transfer of bacteria, viruses
  or other germs from one person to another.
  (touches, coughs on or kisses someone who isn't
  infected).

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Transmission

• Animal to person.
• Being bitten or scratched by an infected animal
  can make you sick and, in extreme circumstances,
  could even cause death. Handling animal waste can
  be hazardous, too. For example, you can acquire a
  toxoplasmosis infection by scooping your cat's
  litter box, particularly if you're pregnant.
• Mother to unborn child.
• A pregnant woman may pass germs that cause
  infectious diseases to her unborn baby. Germs can
  pass through the placenta.

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Transmission

• Indirect contact
• Disease-causing organisms can
• also be passed along by indirect contact.
• Many germs can linger on an inanimate object,
  such as a tabletop, doorknob or faucet handle.
• You can pick up the germs he or she left behind.
  If you then touch your eyes, mouth or nose before
  washing your hands, you may become infected.
• Some infections occur from organisms that
  naturally live in the environment but are not
  passed from person to person. Example anthrax.

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What Causes a Symptom

• Pathogens can over come the defense of your
  immune system, they can multiply causing damage
  to the tissues.
• Viruses can cause death to the cells in which
  they invade
• Toxins are poisons which can be produced by
  microorganisms
• The poisons can be transmitted to the blood
• Some toxins produce fever, destroy blood cells,
  and proteins synthesis

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PATTERNS OF DISEASE

• Center for Disease Control and Prevention (CDC)
• Government Health Department that identify
  pathogens, their method of transmission, and
  geographic distribution
• Endemic Disease disease that is continuously
  present in the population
• Ex. Common cold

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Patterns of Disease

• Epidemic- widespread outbreak of an infectious
  disease many people are infected at the same
  time
• Pandemic- epidemic over a wide geographical area
  "a pandemic outbreak of malaria.

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Treating Disease

• Antibiotics- produced by microorganisms that in
  small amounts will kill or inhibit the growth and
  reproduction of other microorganisms
• Can be used to cure bacterial infections but does
  NOT affect viruses.

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Antibiotic Resistance

• Think back
• What is antibiotic resistance again?

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Immune Response

• The Bodys Fight Against Disease

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The Skin

• 1st line of defense
• Acts as a physical barrier
• How do pathogens enter the skin?

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Body Secretions

• Mucus traps things entering digestive and
  respiratory tracts
• Sweat, Tears, Saliva contain enzyme lysozyme
  that help digest cell wall of some bacteria cells

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Inflammation

• Occurs at the site of an infection
• Fluid leaks into injured tissue helping to
  isolate and destroy pathogens
• Symptoms include redness, swelling, pain, and
  heat
• Inflammation begins when damaged tissue cells and
  white blood cells called basophils release
  histamine.

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Histamine

• Causes blood vessels in the injured area to
  dilate-makes them more permeable to fluid.
• Dilated BV cause the redness of the inflamed
  area.
• Fluid leaks out from the vessels to help destroy
  toxic agents.
• So what is an antihistamine?

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Fever

• Fever refers to an elevation in body
• temperature.
• Normal oral measurement of 98.6 F (37 C)
• Body temperature can also vary up to 1 F (0.6 C)
  throughout the day.
• Fever is not considered medically significant
  until body temperature is above 100.4 F (38 C).
• Fever serves as one of the body's natural
  defenses against bacteria and viruses which
  cannot live at a higher temperature.
• For that reason, low fevers should normally go
  untreated, unless accompanied by troubling
  symptoms.

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White Blood Cells (WBC)

• White Blood Cells- defend against pathogens

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Phagocytes

• White Blood Cells that destroy pathogens by
  surrounding them and engulfing them
• Phagocytes include macrophages, neutrophils,
  monocytes and eosinophils
• Macrophages-found in body tissues
• Others are found in the blood

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Phagocytosis
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The Lines of Defense

• Macrophages- WBC that provide the 1st line of
  defense when pathogens enter the tissues
• If they get past the macrophages the next line is
  neutrophils
• 3rd line- Monocytes -immature macrophages which
  circulate in the blood

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Lines of Defense Cont.

• Monocytes can squeeze through blood vessels to
  the infected area
• Once they reach the infected area they become as
  large as mature macrophages and engulf the dead
  neutrophils and pathogens
• When the infection is over, some monocytes mature
  into tissue macrophages that remain in that area
  to fend of new infections

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PUS

• Fluid that forms at site of infection
• Made of dead macrophages and body fluid
• Formation continues until the infection is over
• Cleared away by macrophages

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Questions

• What is the immune system?
• What does WBC stand for?
• What is the function of a WBC?
• What are some ways that your body fights
  infections?
• How can infections be transmitted?

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Parasites

• An animal or plant that lives in or on a host
  (another animal or plant) it obtains nourishment
  from the host without benefiting or killing the
  host

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Where can parasites be found?

• Can be found in
• Meat
• Unsanitary areas
• Insects (like mosquitoes)
• Fish
• Snails
• Dogs
• Cats
• HUMANS

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28 foot tapeworm
roundworms
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Interesting Facts

• The longest tapeworm ever removed from a human
  came out on September 05, 1991.
• In all, doctors pulled a 37 foot tapeworm out of
  a body through the mouth.
• Whale tapeworms can grow up to 120 feet long.

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Questions

• What is a parasite?
• Where can they be found?
• What makes them a parasite?